Spray gun with pressure operated valve

ABSTRACT

In a spray gun the supply of coating material to the nozzle means of the gun is controlled by a pressure fluid-actuated differential servo piston means dividing the cylinder thereof in a first cylinder chamber around the stem and a second cylinder chamber opposite to the first cylinder chamber. During both strokes of the servo piston means the first cylinder chamber is pressurized by pressure fluid. A maneuvering valve is provided for either supplying pressure fluid to the second chamber for producing one of the strokes of the servo piston means against the action of pressure fluid in the first chamber, or relieving the pressure fluid in the second chamber for releasing the other stroke of the servo piston means under the action of said pressure fluid in the first chamber. More particularly the servo piston means may be of tandem design for quick actuation.

United States Patent [72] lnventor Alt Georg Bertilsson Harlingstorp,Axvall, Sweden [21] Appl. No. 721,304 [22] Filed Apr. 15, 1968 [45]Patented May 25, 1971 [73] Assignee Atlas Copco Aktiebolag Nacka, Sweden[54] SPRAY GUN WITH PRESSURE OPERATED VALVE 3,248,879 5/1966 Natho92/134X FOREIGN PATENTS 821,648 10/1959 Great Britain 91/416 850,49010/1960 Great Britain 91/416 Primary Examiner-Stanley H. TollbergAssistant Examiner-H. S. Lane Attorney-Bauer and Goodman ABSTRACT: In aspray gun the supply of coating material to 6 Claims, 5 Drawing Figs.

the nozzle means of the gun is controlled by a pressure fluid- [52] US.Cl 222/504, actuated diff ti l Servo piston means dividing the cyiinder9l/41625l/31 thereof in a first cylinder chamber around the stern and a[51] Int. Cl B67d 5/06 Second cylinder chamber opposite to the fi tcylinder [50] Field of Search 222/504; chamben During both Strokes f theServo piston means the 92/134; 251/31 63-5; 91/416 first cylinderchamber is pressurized by pressure fluid. A maneuvering valve isprovided for either supplying pressure [56] References Cited fluid tothe second chamber for producing one of the strokes UNITED STATESPATENTS of the servo piston means against the action of pressure fluid2,746,425 5/ 1956 Schafer 91/416X in the first chamber, or relieving thepressure fluid in the 3,083,913 4/1963 Coffman et a1. 239/412X secondchamber for releasing the other stroke of the servo 2,479,454 8/1949Annin 92/134X piston means under the action of said pressure fluid inthe first 2,582,512 1/1952 Stueland. 92/134X chamber. More particularlythe servo piston means may be of 2,983,922 5/ 1961 Juilfs 92/134X tandemdesign for quick actuation.

28 I3 4 26 [2 ll 3 7 /A B 17 l l IO 29 6 l5 PATENTEUHAYZ IQYI 3,580,435

SHEET 3 [IF 3 36 24 34 I6 23 l3 l2 INVIz'N'l'OR.

SPRAY GUN WITH PRESSURE OPERATED VALVE This invention relates to sprayguns for coating materials and more particularly to spray guns havingpressure fluid-actuated servo piston means in the housing of the gun forthe control of the coating material valve therein. Such spray guns arenormally used for airless spraying of coating material under highpressure and for remotely controlling automatic spraying equipmentintended for similar or other spraying operations. Conventionally theservo piston means are moved by a spring during one of the strokes inthe reciprocation thereof and by pressure fluid during the other stroke.

It is an object of the invention to provide in spray guns of the abovetype, a simplified servo piston means in which both strokes of the servopiston means are powered by pressure fluid without actuation of theservo piston means by springs. A further object of the invention is toprovide in spray guns of the above type a servo piston means of a designmore efficient in utilizing the pressure fluid power acting thereagainstfor quick opening or closing of the coating material valve. A stillfurther object is to provide in spray guns of the above type a servopiston means of tandem design without actuating springs.

For the above and other purposes there is according to the inventionprovided a spray gun comprising a housing, nozzle means on said housing,means for supplying coating material under pressure to said nozzlemeans, a coating material valve for controlling the flow of suchmaterial through said nozzle means, a source of pressure fluid, acylinder in said housing, differential servo piston means connected tosaid coating material valve and having a stem portion thereon sealinglybut slidably guided in said housing, said differential servo pistonmeans being movable in said cylinder to perform alternately opening andclosing strokes therein under the action of pressure fluid from saidsource for controlling said coating material valve, said differentialservo piston means dividing said cylinder in a first cylinder chamberaround said stem and a second cylinder chamber opposite to said firstcylinder chamber, means for keeping said first cylinder chamberpressurized by pressure fluid from said source during the strokes ofsaid servo piston means, a maneuvering valve, and means controlled bysaid maneuvering valve for either supplying pressure fluid from saidsource to said second chamber for producing one of the strokes of saidservo piston means against the action of said pressure fluid in saidfirst chamber, or relieving the pressure fluid in said second chamberfor releasing the other stroke of said servo piston means under theaction of said pressure fluid in said first chamber.

The above and other purposes of the invention will become obvious fromthe following description and from the accompanying drawings in whichthree embodiments of the invention are illustrated by way of example. Itshould be understood that these embodiments are only illustrative of theinvention and that various further modifications thereof may be madewithin the scope of the claims.

In the drawings FIG. 1 shows a longitudinal section through a remotelycontrolled automatic spray gun according to one embodiment of theinvention. As depicted in FIG. 1 pressure fluid is supplied to the spraygun via a diagrammatically illustrated maneuvering valve such as to keepthe coating material valve of the spray gun closed. FIG. 2 shows thespray gun in FIG. 1 in another position with the maneuvering valve inrelief position and the coating material valve open. FIG. 3 shows alongitudinal section through an automatic spray gun of modifiedembodiment with the coating material valve therein closed FIG. 4 shows alongitudinal section corresponding to FIG. 3 but with the coatingmaterial valve open. FIG. 5 shows a longitudinal section through a spraygun according to a third embodiment of the invention.

In FIGS. 1 and 2 the housing of the spray gun is designated by and isprovided with a servo piston means consisting of a differential piston13 controlling the flow of paint from/a first, or paint cylinder chamber20. The piston 13 has a stem portion 13 thereon sealingly but slidablyguided in the housing 10 in a bore 29 in free communication with theatmosphere. The piston 13 is journaled for reciprocation in a cylinder14 provided in a backhead 14 which is screwed to the rear end of thespray gun housing 10. The differential piston 13 consists of a resilientpacking cup 15 slidably cooperating with the cylinder 14 and a washer 30retaining the packing cup 15 against a rear shoulder on the steam 13.The washer 30 is locked by a tightening nut screwed onto the stem 13.The packing cup 15 divides the cylinder 14 in two second and thirdcylinder chambers 16, 12 of which said chamber 16 is disposed around thestem 13 and said third chamber 12 is at the end thereof opposite tochamber 16. By means of a conduit 17 the second cylinder chamber 12 isconnectable via a maneuvering valve 11 alternatively to a supply hoseand a source 37 of pressure fluid such as compressed air or to theatmosphere.

By means of a stop screw there is affixed to the stem 13 of differentialpiston 13 the stem 18 of a coating material valve 19. The valve 19 isdisposed in a coating material or paint chamber 20 in the front portionof the housing 10. At the traverse into the paint chamber 20 the coatingmaterial valve stem 18 is surrounded by a sealing ring 28 of packingmaterial which is compressed by the aid of a packing nut 27. Via aconduit 21 the paint chamber 20 is supplied with coating material underhigh pressure of the order of magnitude of 300 atmospheres. The paintchamber 20 has an outlet orifice 31 controlled by the valve 19. Anatomizing nozzle means 25 is kept in place coaxially with and in frontof the outlet orifice 31 by means of a retaining nut 22.

The housing 10 is provided with a cross bore 26 disposed proximate tothe coating material valve axis and serving as a suspending or fixationhole for the housing 10 when the spray gun is to be mounted forautomatized work. I

In FIG. 1 the maneuvering valve 11 is set to a position in whichpressure fluid is supplied from the source 37 via the maneuvering valve11 and conduit 17 to the cylinder chamber 12. The differential piston 13is thus power biased in forward direction towards the outlet orifice 31and the paint valve 19 is maintained firmly on its seat around theoutlet orifice 31. The edge of the packing cup 15 is turned towards thecylinder chamber 16 and in the position depicted in FIG. 1 the cup 15consequently acts as a check valve means allowing pressure fluid to flowto the cylinder chamber 16 while the cylinder chamber 12 is pressurized.When the maneuvering valve 11 is switched to exhaust cylinder chamber12, FIG. 2, the charge of pressure fluid trapped in cylinder chamber 16expands, acts against piston packing cup 15 and displaces thedifferential piston 13 rearwardly away from the outlet orifice 31. Theopening stroke of the coating material valve 19 thus started isamplified by coating material pressure in the paint chamber 20 whichacts on the valve 19 and valve stem 18 axially in the opening directionthereof.

As soon as the maneuvering valve 11 is returned the position indicatedin FIG. 1, the cylinder chamber 12 is again filled by pressure fluid andthe differential piston 13 is moved in its closing stroke forwardlyovercoming the counter pressure in cylinder chamber 16. Cylinder chamber16 is charged at the initial stage simultaneously with chamber 12 bypressure fluid entering chamber 12 and flowing past the packing cup 15.During the closing stroke the differential piston 13 closes the coatingmaterial valve 19 and compresses simultaneously therewith the pressurefluid charge in cylinder chamber 16 to a pressure slightly higher thanline pressure.

In the embodiment depicted in FIGS. 3 and 4 the servo piston means whichat the stem end thereof is affixed to the coating material valve stem18, is of tandem design. In the spray gun housing 32 the servo pistonmeans is thus provided with an outer tandem piston head 13 affixed to astem 13 and sealingly but slidably guided in a partition 34 within thehousing 32. Similar to the embodiment in FIGS. 1, 2 piston head 13 andstem 13 provide a differential piston guided in a bore 14' in a backhead14. In the housing 32 there is provided coaxially with the bore 14 abore 33 in which is slidable an intermediate pistonhead 36 incorporatinga packing cup 35. The intermediate pistonhead 36 is affixed to the stem13 of the pistonhead 13 and is kept in position thereagainst by anextension stem 13 which is screwed onto the forward end of stem 13Between the intermediate pistonhead 36 and the partition 34 there isformed a third cylinder chamber 24 disposed in the bore 33. The secondcylinder chamber 12 in the backhead 14 communicates via inner passages23 provided in the stem 13' with the third cylinder chamber 24.

When pressure fluid is supplied from the source 37 via the maneuveringvalve 1 1 to cylinder chamber 12 in the backhead 14, the packing cup 15will as before act in check valve manner and cylinder chamber 16 betweenthe outer pistonhead 13 and the partition 34 will thus be chargedsimultaneously with pressure fluid entering cylinder chamber 12. As aresult the pistonhead 12 will be actuated by an axial force to performthe closing stroke of the tandem piston in the direction of the outletorifice 31 of the coating material valve 19. This force is amplified bythe cylinder chamber 24 between the packing cup 35 of pistonhead 36 andthe partition 34 becoming pressurized simultaneously with chamber 12 viathe passages 23, and the tandem piston will thus perform its closingstroke under pressure bias against both pistonheads 13, 36.

As soon as the maneuvering valve 11 is switched to exhaust position,FIG. 4, the cylinder chambers 24 and 12 will be exhausted. Pressurefluid trapped in cylinder chamber 16 behind the packing cup 15 will nowbe free to expand for performing the opening stroke of the tandem pistonand for opening the coating material valve 19. The opening movement isamplified by coating material pressure starting to act in the paintchamber on the coating material valve 19 in the opening directionthereof as soon as the valve 19 has left its seat around orifice 31. Thetandem design of the servo piston means increases the total piston areaavailable for the closing stroke and reduces the dimensions of the servopiston means allowing quick operation.

in the embodiment exemplified in FIG. 5 the servo piston means in thespray gun housing 38 is identical in operation with the embodimentdepicted in FIGS. 3,4 The backhead 14, however, is closed at the rearend thereof by means of a plug 39 and pressure fluid is supplied to thetandem piston for closing purposes from the source 37 directly to bothcylinder chambers 24, 16. The supply of pressure fluid is controlled bya maneuvering valve 40 which is actuated by a trigger 41 and may bemoved against the action of a spring 42 from a position a in which thesource 37 is connected to both cylinder chambers 24, 16 to a position bin which cylinder chamber 16 is connected to the source 37 whilst thecylinder chamber 24 is exhausted via a conduit 43. Via the passages 23cylinder chamber 12 is of course exhausted simultaneously with cylinderchamber 24. In connection with the depicted valve arrangement it isparticularly suitable to arrange the maneuvering valve 40 in a pistoltype grip 44, diagrammatically depicted by broken lines in FIG. 5, bywhich the spray gun housing 38 may be directed and used manually.

I claim:

1. A spray gun comprising a housing, nozzle means on said housing,meansfor supplying coating material under pressure to said nozzle means,a piston operating in said housing, a coating material valve mounted onan end of said piston within a first cylinder chamber for controllingthe flow of such material through said nozzle means, a source ofpressure fluid, an additional cylinder in said housing, a differentialservo pistonhead connected to said piston at an end opposite to saidcoating material valve, said piston having an intermediate stem portionthereon sealing but slidably guided in said housing, said differentialservo pistonhead being movable in said additional cylinder to performalternately opening and closing strokes therein under the action ofpressure fluid from said source for controlling said coating materialvalve, said differential servo pistonhead dividing said additionalcylinder in a second cylinder chamber around said stern and a thirdcylinder chamber ad'acent to said second cylinderchamber, a passageconnected etween said second and third cylinder chambers, a one-wayvalve means arranged in said passage for controlling the flowing ofpressure fluid only in the direction from said third cylinder chamberinto said second cylinder chamber, means for flowing pressure fluid fromsaid source into said third cylinder chamber and from thence throughsaid one-way valve means into said second cylinder chamber, amaneuvering valve, and means controlled by said maneuvering valvefor'either supplying pressure fluid from said source to said thirdchamber for producing said closing stroke of said servo piston headagainst the action of said pressure fluid in said first and secondchambers, or relieving the pressure fluid in said third chamber forreleasing said servo piston head for said opening stroke thereof underthe action of pressure fluid in said first and second chambers.

2. A spray gun according to claim 1 in which said maneuvering valve hasa first position adapted to cause said means controlled thereby tosupply pressure fluid to all three of said cylinder chambers and asecond position adapted to supply pressure to said first cylinderchamber only and to relieve the pressure in said third cylinder chamber.

3. A spray gun comprising a housing, nozzle means on said housing, meansfor supplying coating material under pressure to said nozzle means, acoating material valve for controlling the flow of such material throughsaid nozzle means, a source of pressure fluid, a cylinder in saidhousing, a tandem piston having a stem portion thereon connected to saidcoating material valve, said tandem piston having an intermediate and anouter piston head thereon and being movable in said cylinder to performalternately opening and closing strokes therein under the action ofpressure fluid from said source for controlling said coating materialvalve, a partition in said housing between said piston heads forsealingly but slidably receiving said stem portion therein, said tandempiston dividing said cylinder in a first cylinder chamber between saidpartition and outer head, a second cylinder chamber outwardly of saidouter head, and a third cylinder chamber between said partition andintermediate head, passage means permanently communicating said secondand third cylinder chambers, means for keeping said first cylinderchamber pressurized by pressure fluid from said source during thestrokes of said tandem piston, a maneuvering valve, and means controlledby said maneuvering valve for either supplying pressure fluid from saidsource to said second and third chambers for producing one of thestrokes of said tandem piston against the action of said pressure fluidin said first chamber, or relieving the pressure fluid in said secondand third chambers for releasing the other stroke of said tandem pistonunder the action of pressure fluid in said first chamber.

4. A spray gun according to claim 3 in which said means for keeping saidfirst cylinder chamber pressurized are check valve means on said outerhead opening for pressure fluid flow from said second to said firstcylinder chamber, said check valve means being provided by a resilientpacking cup included in said outer head.

5. A spray gun according to claim 3 in which said passage means areprovided in said stem portion.

6. A spray gun according to claim 3 in which said maneuvering valve hasa first position adapted to cause said means controlled thereby tosupply pressure fluid to all three of said cylinder chambers and asecond position adapted to supply pressure to said first cylinderchamber only and to relieve the pressure in said second and thirdcylinder chambers.

1. A spray gun comprising a housing, nozzle means on said housing, meansfor supplying coating material under pressure to said nozzle means, apiston operating in said housing, a coating material valve mounted on anend of said piston within a first cylinder chamber for controlling theflow of such material through said nozzle means, a source of pressurefluid, an additional cylinder in said housing, a differential servopistonhead connected to said piston at an end opposite to said coatingmaterial valve, said piston having an intermediate stem portion thereonsealing but slidably guided in said housing, said differential servopistonhead being movable in said additional cylinder to performalternately opening and closing strokes therein under the action ofpressure fluid from said source for controlling said coating materialvalve, said differential servo pistonhead dividing said additionalcylinder in a second cylinder chamber around said stem and a thirdcylinder chamber adjacent to said second cylinder chamber, a passageconnected between said second and third cylinder chambers, a one-wayvalve means arranged in said passage for controlling the flowing ofpressure fluid only in the direction from said third cylinder chamberinto said second cylinder chamber, means for flowing pressure fluid fromsaid source into said third cylinder chamber and from thence throughsaid one-way valve means into said second cylinder chamber, amaneuvering valve, and means controlled by said maneuvering valve foreither supplying pressure fluid from said source to said third chamberfor producing said closing stroke of said servo piston head against theaction of said pressure fluid in said first and second chambers, orrelieving the pressure fluid in said third chamber for releasing saidservo piston head for said opening stroke thereof under the action ofpressure fluid in said first and second chambers.
 2. A spray gunaccording to claim 1 in which said maneuvering valve has a firstposition adapted to cause said means controlled thereby to supplypressure fluid to all three of said cylinder chambers and a secondposition adapted to supply pressure to said first cylinder chamber onlyand to relieve the pressure in said third cylinder chamber.
 3. A spraygun comprising a housing, nozzle means on said housing, means forsupplying coating material under pressure to said nozzle means, acoating material valve for controlling the flow of such material throughsaid nozzle means, a source of pressure fluid, a cylinder in saidhousing, a tandem piston having a Stem portion thereon connected to saidcoating material valve, said tandem piston having an intermediate and anouter piston head thereon and being movable in said cylinder to performalternately opening and closing strokes therein under the action ofpressure fluid from said source for controlling said coating materialvalve, a partition in said housing between said piston heads forsealingly but slidably receiving said stem portion therein, said tandempiston dividing said cylinder in a first cylinder chamber between saidpartition and outer head, a second cylinder chamber outwardly of saidouter head, and a third cylinder chamber between said partition andintermediate head, passage means permanently communicating said secondand third cylinder chambers, means for keeping said first cylinderchamber pressurized by pressure fluid from said source during thestrokes of said tandem piston, a maneuvering valve, and means controlledby said maneuvering valve for either supplying pressure fluid from saidsource to said second and third chambers for producing one of thestrokes of said tandem piston against the action of said pressure fluidin said first chamber, or relieving the pressure fluid in said secondand third chambers for releasing the other stroke of said tandem pistonunder the action of pressure fluid in said first chamber.
 4. A spray gunaccording to claim 3 in which said means for keeping said first cylinderchamber pressurized are check valve means on said outer head opening forpressure fluid flow from said second to said first cylinder chamber,said check valve means being provided by a resilient packing cupincluded in said outer head.
 5. A spray gun according to claim 3 inwhich said passage means are provided in said stem portion.
 6. A spraygun according to claim 3 in which said maneuvering valve has a firstposition adapted to cause said means controlled thereby to supplypressure fluid to all three of said cylinder chambers and a secondposition adapted to supply pressure to said first cylinder chamber onlyand to relieve the pressure in said second and third cylinder chambers.